Re: [PATCH, PR 49094] Refrain from creating misaligned accesses in SRA

[Martin Jambor]

Hi,

I had to add a test that the analyzed expression is not an SSA name.
This has been approved by Rchi on IRC yesterday.  Thus, I have
committed the following as revision 175703 after successful run of c
and c++ testsuite on sparc64 (and a bootstrap and test with another
patch on x86_64-linux).

Thanks,

Martin


2011-06-30  Martin Jambor  <mjam...@suse.cz>

        PR tree-optimization/49094
        * tree-sra.c (tree_non_mode_aligned_mem_p): New function.
        (build_accesses_from_assign): Use it.

        * testsuite/gcc.dg/tree-ssa/pr49094.c: New test.


Index: src/gcc/tree-sra.c
===================================================================
--- src.orig/gcc/tree-sra.c
+++ src/gcc/tree-sra.c
@@ -1050,6 +1050,26 @@ disqualify_ops_if_throwing_stmt (gimple
   return false;
 }
 
+/* Return true iff type of EXP is not sufficiently aligned.  */
+
+static bool
+tree_non_mode_aligned_mem_p (tree exp)
+{
+  enum machine_mode mode = TYPE_MODE (TREE_TYPE (exp));
+  unsigned int align;
+
+  if (TREE_CODE (exp) == SSA_NAME
+      || mode == BLKmode
+      || !STRICT_ALIGNMENT)
+    return false;
+
+  align = get_object_alignment (exp, BIGGEST_ALIGNMENT);
+  if (GET_MODE_ALIGNMENT (mode) > align)
+    return true;
+
+  return false;
+}
+
 /* Scan expressions occuring in STMT, create access structures for all accesses
    to candidates for scalarization and remove those candidates which occur in
    statements or expressions that prevent them from being split apart.  Return
@@ -1074,7 +1094,10 @@ build_accesses_from_assign (gimple stmt)
   lacc = build_access_from_expr_1 (lhs, stmt, true);
 
   if (lacc)
-    lacc->grp_assignment_write = 1;
+    {
+      lacc->grp_assignment_write = 1;
+      lacc->grp_unscalarizable_region |= tree_non_mode_aligned_mem_p (rhs);
+    }
 
   if (racc)
     {
@@ -1082,6 +1105,7 @@ build_accesses_from_assign (gimple stmt)
       if (should_scalarize_away_bitmap && !gimple_has_volatile_ops (stmt)
          && !is_gimple_reg_type (racc->type))
        bitmap_set_bit (should_scalarize_away_bitmap, DECL_UID (racc->base));
+      racc->grp_unscalarizable_region |= tree_non_mode_aligned_mem_p (lhs);
     }
 
   if (lacc && racc
Index: src/gcc/testsuite/gcc.dg/tree-ssa/pr49094.c
===================================================================
--- /dev/null
+++ src/gcc/testsuite/gcc.dg/tree-ssa/pr49094.c
@@ -0,0 +1,38 @@
+/* { dg-do run } */
+/* { dg-options "-O" } */
+
+struct in_addr {
+       unsigned int s_addr;
+};
+
+struct ip {
+       unsigned char ip_p;
+       unsigned short ip_sum;
+       struct  in_addr ip_src,ip_dst;
+} __attribute__ ((aligned(1), packed));
+
+struct ip ip_fw_fwd_addr;
+
+int test_alignment( char *m )
+{
+  struct ip *ip = (struct ip *) m;
+  struct in_addr pkt_dst;
+  pkt_dst = ip->ip_dst ;
+  if( pkt_dst.s_addr == 0 )
+    return 1;
+  else
+    return 0;
+}
+
+int __attribute__ ((noinline, noclone))
+intermediary (char *p)
+{
+  return test_alignment (p);
+}
+
+int
+main (int argc, char *argv[])
+{
+  ip_fw_fwd_addr.ip_dst.s_addr = 1;
+  return intermediary ((void *) &ip_fw_fwd_addr);
+}